trochoid

adjective

• 1 Anatomy denoting a joint in which one element rotates on its own axis (e.g., the atlas vertebra).

• 2 Geometry denoting a curve traced by a point on a radius of a circle rotating along a straight line or another circle (a cycloid, epicycloid, or hypocycloid).

• 3 Zoology having or denoting a form of mollusk shell that is conical with a flat base, like a top shell.

noun

• 1a trochoid curve.

• 2a trochoid joint.